Why are tropical lowlands generally warmer than polar regions?

Answer: Sunlight is more concentrated because it arrives at a higher angle

The tropics are much closer to the Sun than the poles — The difference in distance to the Sun across Earth is tiny compared with Earth’s distance from the Sun. The angle of incoming sunlight, not a large distance difference, explains the broad latitude pattern.

Sunlight is more concentrated because it arrives at a higher angle ✓ — Over the year, sunlight reaches the tropics at higher angles and spreads over less ground than at the poles. This gives the tropics more solar energy per unit area on average. The Sun is not directly overhead there all day or all year, and high mountains can still be cold.

The ground releases much more heat from Earth’s interior there — Heat from Earth’s interior is much smaller than the solar energy shaping this climate pattern. The tropics receive more concentrated sunlight; they are not generally warmer because the ground acts as a stronger heater.